assuming that it was a mk4 gti, it could have intake, chip, and exhaust.. most of the good exhausts for mk4 jetta/golfs arent very noticeable and tend to look stock. he mightve had a new intake manifold, new spark plugs.. you never know.. theres not much you can do inexpensively to gain a lot of hp with the VR6 engine.. he probably did not have a header.